To address a couple of those points:
FIFA actually uses "studs showing" especially in the context of making contact with the opponent in their instructional material. They also push toward "striking of cleats against foot" is (typically) reckless, while cleats against body above ankle is (typically) considered excessive force. Of course, those are really starting points for your considerations to determine what level an offence is.
In this case (for me), the intensity of the tackle is medium-high, but I'm not 100% convinced that it's high enough for dismissal. With where the initial contact takes place (relatively high on the shin), despite being in a glancing manner only (as compared to the crunching Coleman tackle), I can understand why red was shown in this instance.
Combined with the follow-through with the trail foot in a manner that almost looks like it's lashing out at the opponent's other foot (right at the end of the tackle), seeing the referee go red on this tackle is understandable.
I can definitely see an argument for a caution on this play, and I'll admit that my first couple of viewings, I lean towards yellow. With more viewings, I find myself waffling more between caution and dismissal on the play, but like I said above, I understand why the referee dismissed Larsson.